Whether you're upgrading obsolete wiring, adding more lights or undertaking a major remodel, it's important to make a plan before rewiring a room. You can often get all the power you need from a single circuit, but you may need more than one if you plan to plug in one or more power-hungry appliances. Each circuit needs the protection of a circuit breaker in the main panel, and the size of the breaker depends on the load.

1

Locate the breakers in the main panel that control the existing lights and outlets in the room and turn them off. If the breakers aren't labeled, you may need someone to help you by checking the lights while you flip them off one by one. Test all the outlets to ensure they're dead by plugging a working lamp into each one and turning it on; it should not turn on.

2

Note which lights and outlets in other rooms are controlled by the breakers you turned off. If you want to leave the circuits to those devices unchanged, you'll have to determine the points where they connect to the room you are rewiring. If any are closer to the panel, power to the circuits you are rewiring may be drawn from them, and it may be convenient to preserve the connection.

3

Disconnect the circuits in the room. This may involve removing a connection from an outlet or switch in another room, or it may involve removing a circuit breaker. Get the help of an electrician if you aren't comfortable working in the panel to remove a breaker.

4

Unscrew the cover plates from all outlets and switches you plan to move with a screwdriver. Unscrew the outlets and switches from the electrical boxes, which are the metal or plastic boxes to which they are attached. Disconnect the wires either by unscrewing them from the terminal screws or snipping them with wire snippers. Take down any lights you want to move and disconnect the wires.

5

Pull out the disconnected wires. Some of them will probably be stapled to studs or ceiling rafters, and if you don't have access to the staples, you may have to cut the wires and leave sections buried in the walls.

6

Draw a diagram of your new circuitry and add up the loads to determine how many circuits you need and the number of breakers you need to control them. The load in watts is specified on each device, either on a plate attached to it or, in the case of a light bulb, on the packaging or on the top of the bulb. Once you know the total load on a circuit, divide it by 120 volts to obtain the current draw. The breaker for that circuit should be rated for at least that amount of current. Don't forget to add the loads of devices in other rooms that will be on the circuits you are rewiring.

7

Cut a hole in the drywall with a drywall saw for each new switch, outlet or light fixture you plan to install. The hole should be the exact size of the electrical box you plan to install there, but you'll have to oversize it to give yourself enough room to nail it to a stud or rafter.

8

Run the new wires and pull them through the backs of the electrical boxes. Getting wires behind existing drywall can be challenging. It's often best to run them through the attic or basement, drill a 1/2-inch hole in the top or bottom plate of the wall and pass them vertically to each box. Staple lateral runs of wire to joists or rafters with wire staples.

9

Use 12-gauge wire for all 120-volt circuits. Although the code allows 14-gauge wire for circuits drawing 15 amps or less, using thicker wire for all the circuits is safer and it will prevent inadvertent wiring of a circuit with two different sizes of wire, which is prohibited. If you're drawing power from a circuit with 14-gauge wire, however, continue to use wire of that size.

10

Pull the wires through the back of each electrical box, strip the ends and connect each device. Screw the device to the electrical box and screw on a cover plate. Once all the devices are installed, connect each new circuit, either by wiring it to a device in another room or by wiring it to a breaker and installing the breaker into the panel.

11

Turn on each breaker that controls one of the new circuits and verify that it stays on. If it trips, leave it off and check your connections.

Things You Will Need

Test lamp

Screwdriver

Wire snippers

Drywall saw

Electrical boxes

12-gauge electrical wire

Drill

1/2-inch drill bit

Wire staples

Tips

Each 240-volt appliance that you plan to install, such as an air conditioner, must be on a dedicated circuit and should be wired by a licensed electrician.

If you are upgrading ungrounded circuitry, you may also need to upgrade your panel. This is a job best undertaken by an electrician.

Avoid oversizing holes for electrical boxes by using remodeling boxes whenever possible. They attach directly to the drywall.

Warnings

Be sure to test every device in the room before disconnecting it. There may be one on a branch circuit that originates in another part of the house.

Check with your building department before starting work. You may need a permit.

About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.